International Journal of Reproduction, Contraception, Obstetrics and Gynecology
Mallikarjuna M et al. Int J Reprod Contracept Obstet Gynecol. 2015 Dec;4(6):1720-1725
www.ijrcog.org
DOI: http://dx.doi.org/10.18203/2320-1770.ijrcog20151130
pISSN 2320-1770 | eISSN 2320-1789
Research Article
Estimation of fetal weight in utero by Dawn's formula and Johnson's
formula: a comparative study
Mallikarjuna M.1*, Rajeshwari B.V.2
1
Department of Obstetrics & Gynaecology, Subbaiah Institute of Medical Sciences, Shimoga, Karnataka, India
Department of Obstetrics & Gynaecology, Kamineni Institute of Medical Sciences, Narketpally, Nalgonda,
Telangana, India
2
Received: 25 September 2015
Revised: 12 October 2015
Accepted: 28 October 2015
*Correspondence:
Dr. Mallikarjuna M.,
E-mail: [email protected]
Copyright: © the author(s), publisher and licensee Medip Academy. This is an open-access article distributed under
the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial
use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Background: Survival of the premature infant has been shown to be related more to fetal weight than to any other
consideration. A lot of work has been done to find out accurate methods for estimation of fetal size and weight in
utero.
Methods: This study consists of total 200 case studies included patient of different parity all delivered in these
hospitals either vaginally or by caesarian section. Two methods of estimation of birth weight were assessed and
compared.
Results: 33.5% of cases were within ±100gms by Johnson's formula, whereas in Dawn's formula 51.5% cases were
within +100 gm of actual birth weight.73% of cases by Johnson's formula were within ±250 gms and 88.5% of cases
by Dawn's formula were within ±250 gms of actual birth weight.91% of cases by Johnson's formula and 99% of cases
by Dawn's formula were within ±500 gms of actual birth weight.
Conclusions: Dawn's formula was found to be more accurate (88.5% within ±250 gms) than Johnson's formula
(53.5% within ±250 gms) in prediction of antenatal fetal weight.
Keywords: Birth weight, Johnson formula, Dawn formula
INTRODUCTION
caesarean section, interruption of pregnancy in the
treatment of toxaemia and diabetes.
Estimation of fetal weight in utero has become increasing
important in regard to the prevention of prematurity and
in evaluation of fetopelvic disproportion where a large
baby is suspected, induction of labour before term, in
complications of pregnancy and detection of intrauterine
growth retardation.
A lot of work has been done to find out accurate methods
for estimation of fetal size and weight in utero. These
include clinical methods, x-ray of foetus in utero, external
measurement of uterus and ultrasound techniques.1-7
Survival of the premature infant has been shown to be
related more too fetal weight than to any other
consideration. Obstetrician is faced with estimation of the
fetal weight when interruption of pregnancy is considered
at a relatively elective time. These occasions arise with
conservative management of placenta praevia, repeat
The present study was aimed at estimation of fetal weight
in utero by Dawn's formula as well as by Johnson's
formula and to study a comparative evaluation of the two
formulas.8,9
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METHODS
Method of measurement: Johnson's formula
A total number of 200 patients were included in this
study. All these patients were admitted in the labour ward
of Govt. General Hospital, Sangameshwar Teaching &
General Hospital attached to M. R. Medical College,
Gulbarga.
Measurements were made during uterine relaxation of the
patient were in labour. Measurement was made from the
upper edge of the symphysis pubis following the
curvature of the abdomen with a tape; the upper hand was
placed firmly against the top of the fundus with the
measuring tape passing between the index and middle
fingers. Readings were taken from the perpendicular
intersection of the tape with the fingers.
Selection of cases
This study consists of total 200 case study included
patient of different parity all delivered in these hospitals
either vaginally or by caesarian section.
The station of the head was assured by pelvic
examination.
Inclusion criteria
Procedure
1.
2.
Fetal weight estimation by Johnson’s formulae.
Single fetus with vertex presentation
Gestational age more than 28 week
Exclusion criteria
1.
2.
3.
Congenital malformation
Multiple pregnancy
Malpresentation
Examination method
All the patients studied were selected randomly after
thorough clinical examination.
Fetal weight in grams
= (Fundal height in cms - 11 or 12 or 13) According to
station x 155
When station presenting part at the level of Ischial spines
(zero station) 12 was subtracted from fundal height in
cms, when above the level of ischial spine (minus station)
13 and when below the level of ischial spines (plus
station) 11 was subtracted from fundal height.
If women weight more than 200 patients (90 kg), 1 is
subtracted from the fundal height.
History
Fetal weight estimation by Dawn's formula.
A detailed history of present pregnancy in terms of parity,
period of amenorrhea, regularity of cycles, history
regarding illness or pregnancy associated complications
was asked. An account of menstrual, obstetrical and
medical history is noted.
Clinical examination
A general and systemic examination is conducted.
Obstetrical examination included SFH, Maximal vertical
length of uterus, maximal for diameter of uterus, double
abdominal wall thickness, fetal lie, attitude, presentation,
position and station.
Routine investigation
1.
2.
3.
4.
H6%
Blood grouping and typing
VDRL
Urine routine
Instruments used
1.
2.
Pelvimeter
Non-elastic measuring tape
With pelvimeter, vertical length of gravid uterus is
measured from superior border of symphysis pubis to
fundus-L in cm that of transverse diameter at uterine
cornu-(T) in cm.
Double abdominal wall thickness (DAWT) is measured
by pelvimeter for correction of h. & T, finally measures
of L & T are fed in formula L x (1/2 T)2 x 1.44. Fetal
weight in gm is calculated.
Procedure
The measurements are taken from 28 weeks onwards till
42 weeks when vertex lies on the pelvic brim.
Standing on the right of pregnant women, superior border
of symphysis pubis and summit of uterine fundus are
palpated by two fingers. Abdominal skin at uterine
fundus is marked with pen. One limb end of pelvimeter is
pressed against superior border of symphysis pubis while
the other limb end is pressed against uterine fundus. The
measure read on pelvimeter is vertical length (L) is cure.
RESULTS
In this study 200 patients admitted to labour room were
selected as study group. Patients were selected randomly.
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Patient with single lives fetus, of more than 28 were
gestation, with vertex patient without obstetric
complicative were included. Also cases of multiple
pregnancies, malpresentation were excluded.
Upon delivery, actual birth weight of the baby was
recorded. The birth weight of the babies fell into 6
categories (Table-4). The largest group of patients
delivered babies between 2500-2999 gms.
Results were evaluated and analysed with respect to age,
parity, gravide, gestational weeks. A comparative
analysis of fetal weights assessed by Johnson's and
Dawn's methods was made.
Table 4: Actual birth weight.
Accuracy of the Johnson's and Dawn's method was
evaluated using the actual birth weight of baby after
delivery as the standard.
In the present study of 200 cases 38% of cases were
booked and 62% of cases were unbooked.
In the present study, most of the patients were from
middle socio-economic status i.e. 56% followed by low
40% and 4% were high socioeconomic status.
Out of 200 cases, 30% of cases were less than 20 years of
age, 67% were between 21 to 30 years. 3% of cases were
of above 30 years of age (Table-1).
Birth weight
< 2000 gms
2001 to 2499 gms
2500 to 2999 gms
3000 to 3499 gms
3500 to 3999 gms
4000 gms and above
Total
Frequency
05
35
102
42
14
02
200
Table 5: Fetal weight estimation by Johnson's
formula.
Parity
Primi
G2
G3
≥G4
±100
26
15
20
06
%
30.5
34
35.7
40
±250
49
21
26
11
%
57.6
47.7
46.4
73.5
±500
78
39
50
15
%
91.7
88.6
89.2
100
Table 1: Age distribution.
Age group
≤20 years
21 – 25 years
26 – 30 years
31 – 35 years
Total
Frequency
60
83
51
06
200
Percentage
30.0
41.5
25.5
03.0
100
Out of 200 cases, 13% of cases were of less than 37
weeks of gestation, 86% were of 37 — 40 weeks and 1%
were of > than 40 weeks (Table 2).
Table 2: Period of gestation.
Gestation
<37 weeks
37 – 40 weeks
>40 weeks
Total
Frequency
26
172
02
200
Percentage
13
26
01
100
Out of 200 cases, 42.5% were of primi gravida, 50%
were multi gravida and 7.5% were of cases were of grand
multiparas (Table-3).
Table 3: Parity of patients.
Parity
Primi
G2
G3
≥G4
Total
Frequency
85
44
56
15
200
Percentage
42.5
22
28
07.5
100
On comparing the fetal weight estimated by Johnson's
formulae with the actual birth weight, the following
observations were made.
Primi: total number of patients 85
Out of 85 primi, in 26 cases i.e., 30.5% the fetal weight
estimated were within ±100 gms of actual birth weight.
In, 49 cases i.e., 57.6% the fetal weight estimated were
within ±250gm of actual birth weight. In 78 cases i.e.,
91.76%, the fetal weight estimated were within ±500 gms
of actual birth weight.
G2: total number of capes 44
In 15 cases i.e., 34% the fetal weight estimated were
within ±100 gms of actual birth weight.
In 21 cases i.e., 47.7%, the fetal weight estimated were
within ±250 gms of actual birth weight.
In 39 cases i.e., 88.6% the fetal weight estimated were
within ±500 gms of actual birth weight.
G3: total number of cases 56
In 20 cases i.e., 35.7% the fetal weight estimated were
within ±100 gms of actual birth weight.
In 26 cases i.e., 46.4% the fetal weight estimated were
within ±250 gms of actual birth weight.
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In 50 cases i.e., 89.2% the fetal weight estimated were
within ±500 gms of actual birth weight.
G2: total number of cases 44
≥G4: total number of cases 15
In 24 cases i.e., 54.5% the fetal weight estimated were
within ±100gm of actual birth weight.
In 6 cases i.e., 40%, the fetal weight estimated were
within ±100 gms of actual birth weight.
In 39 cases i.e., 88.6% the fetal weight estimated were
within ±250gm of actual birth weight.
In 11 cases i.e., 73.3% the fetal weight estimated were
within ±250 gms of actual birth weight.
In 43 cases i.e., 97.7% the fetal weight estimated were
within ±500gm of actual birth weight.
In 15 cases i.e., 100% the fetal weight estimated were
within ±500 gms of actual birth weight.
G3: total number of cases 56
In 67 cases out of 200 cases studied i.e., 33.5%, the fetal
weight estimated by Johnson's formula were within ±100
gms if actual birth weight.
In 107 cases, i.e., 53.5% the fetal weight estimated by
Johnson's formula were within ±250 gms of actual birth
weight.
In 182 cases i.e., 91% the fetal weight estimated were
within ±500 gms of actual birth weight.
Table 6: Difference between actual birth weight and
estimated birth weight.
Difference B/w Actual
and estimated
±100
±250
±500
Frequency
Percentage
67
107
182
33.5
53.5
91
±100
46
24
24
09
%
54.1
54.5
42.8
60
±250
80
39
43
15
%
94.1
88.6
76.7
100
±500
85
43
55
15
In 43 cases i.e., 76.7% the fetal weight estimated were
within ±250gm of actual birth weight.
In 55 cases i.e., 98.2% the fetal weight estimated were
within ±500gm of actual birth weight.
>G4: total number of cases 15
In 9 cases i.e., 60% the fetal weight estimated were
within ±100gm of actual birth weight.
In 15 cases i.e., 100% the fetal weight estimated were
within ±250gm of actual birth weight.
In 15 cases i.e., 1000/o the fetal weight estimated were
within ±500gm of actual birth weight.
Table 7: Fetal weight estimations by Dawn's formula.
Parity
Primi
G2
G3
≥G4
In 24 cases i.e., 42.8% the fetal weight estimated were
within ±100gm of actual birth weight.
%
100
97.7
98.2
100
Table 8: Difference between actual birth weight and
estimated birth weight by Dawn's formula.
Difference B/w Actual
and estimated
±100
±250
±500
Frequency
Percentage
103
177
198
51.5
88.5
99
On comparing the fetal weight estimated 'by Dawn's
formula with the actual I birth weight, the following
observations were made.
In 103 cases out of 260 cases studied i.e., 1.5%, the fetal
weight estimated by Dawn's formula were within ±100
gms if actual birth weight.
Primi: total number of cases 85
In 177 cases, i.e., 88.5% the fetal weight estimated by
Dawn's formula were within ±250 gms of actual birth
weight.
Out of 85 primi in 46 cases i.e., 54.1% the fetal weight
estimated were within +100 gms of actual birth weight.
In 80 cases i.e., 94.1%, the fetal weight estimated were
within ±250gm of actual birth weight.
In 198 cases i.e., 99% the fetal weight estimated by
Dawn's formula were within ±500 gms of actual birth
weight.
In 85 cases i.e., 100%, the fetal weight estimated by
Johnson's formula were within ±500gm of actual birth
weight.
33.5% of cases were within ±100gms by Johnson's
formula, whereas in Dawn's formula 51.5% cases were
within +100 gm of actual birth weight.
International Journal of Reproduction, Contraception, Obstetrics and Gynecology
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Mallikarjuna M et al. Int J Reprod Contracept Obstet Gynecol. 2015 Dec;4(6):1720-1725
73% of cases by Johnson's formula were within ±250
gms and 88.5% of cases by Dawn's formula were within
±250 gms of actual birth weight.
91% of cases by Johnson's formula and 99% of cases by
Dawn's formula were within ±500 gms of actual birth
weight.
As can be observed from table-13, it is found that, mean
actual birth weight of 2777.57, Johnson's has a mean of
2851.4 and the standard deviation of 350.70 gms standard
error of 38.98 gms.
gms accuracy by Dawn's formula was 51.5% as
compared to Johnson's formula of 38.5%, at ±250 gms it
was 88.5% by Dawn's formula and 53.5% by Johnson's
formula and at ±500 gms. 99% by Dawn's formula and
91% by Johnson's formula.
This can be explained by the facts that
1.
2.
For Dawn's formula, the mean weight is 2744.48 for the
actual birth weight of 2777.57. The standard deviation is
392.39 gm and the standard error is 40.9.
Probability value (p) is not statistically significant in case
of both Johnson's and Dawn's formula of compared to
actual birth weight.
Table 9: Comparing the estimated fetal weight by
Dawn's formula and Johnson's formula.
Formulae
Johnson's
formula
Dawn's
formula
% of cases
within
±100
% of cases
within
±250
% of cases
within
±500
51.5%
88.5%
99%
38.5%
53.5%
91%
3.
In Dawn's formula, both vertical and transverse
diameters of uterus are measured while in Johnson's
formula only vertical length of the uterus is taken
into consideration.
D'arble abdominal wall thickness is taken into
consideration in Dawn's formula, so that it helps
incorrecting the vertical and transverse diameter of
the uterus because DAWT effects the measurements
of these diameters of uterus. But in Johnson formula
DAWT is not taken into, consideration. So the
vertical length of uterus which is measured per
abdomen may not correspond with the exact vertical
length of the uterus.
Both these procedures are simple to perform.
However in Dawn's formula determination of station
by Per Vaginal (P/V) examination is not required but
for Johnson's formula this is needed.
Johnson's formula can be applied irrespective of station
of presenting part but Dawn's formula should be applied
as recommended by the author, only in those cases where
vertex sits just at the brim i.e., neither free floating nor
deeply engaged.
DISCUSSION
CONCLUSIONS
By Johnson's formula the actual birth weight was
accurate within ±250 gms of predicted portal weight in
53.5%. Present study results are similar to those of
Johnson's and Tostach9 and Vimila and Sushila studies.10
Antenatal fetal weight can be estimated with reasonable
accuracy by Dawn's formula and Johnson's formula. Both
the methods are simple, safe easy to perform,
economical, without any on comparative evaluation of
the two, Dawn's formula was found to be more accurate
(88.5% within ±250 gms) than Johnson's formula (53.5%
within ±250 gms) in prediction of antenatal fetal weight.
By Dawn's formula present study had 88.5% within ±250
gms of actual birth weight which is similar to that of
Vimila and Sushila who reported 81% of cases within
±250 gms of actual birth weight whereas Dawn et al
reported 100% within 10% of actual birth weight.10
Comparing the results in present study, the results of
Johnson's formula are consistent with the results of
author, while for Dawn's formula the results are 58.5% as
compared to 100% results of the authors8 (Dawn et al,
1983).9
Comparative evaluation of Dawn's formula and Johnson's
formula:
In present study, the prediction of fetal weight in utero by
Dawn's formula has been found definitely better than
Johnson's formula because the total accuracy of fetal
weight prediction by Dawn's formula exceeded that of
Johnson's formula at all level of differences. i.e., at ±100
Funding: No funding sources
Conflict of interest: None declared
Ethical approval: The study was approved by the
Institutional Ethics Committee
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Cite this article as: Mallikarjuna M, Rajeshwari BV.
Estimation of fetal weight in utero by Dawn's
formula and Johnson's formula: a comparative study.
Int J Reprod Contracept Obstet Gynecol
2015;4:1720-5.
International Journal of Reproduction, Contraception, Obstetrics and Gynecology
Volume 4 · Issue 6 Page 1725